Data Processing for the Sudbury Neutrino Observatory

Aksel Hallin

Queen’s,

October 2006

Sudbury Neutrino Observatory

1700 tonnes InnerShielding H2O

1000 tonnes D2O ($300 M)

5300 tonnes Outer Shield H2O

12 m Diameter Acrylic Vessel

Support Structure for 9500 PMTs, 60% coverage

Urylon Liner andRadon Seal

Unique Signatures in SNO (D2O)

Charged-Current (CC)e+d e-+p+pEthresh = 1.4 MeV

ee onlyonly

Elastic Scattering (ES)x+e- x+e-

x, but enhanced for e

Neutral-Current (NC) x+d x+n+p Ethresh = 2.2 MeV

Equally sensitive to Equally sensitive to e e

3 ways todetect neutrons

Numerical tools for SNO

• “Data Cleaning”

• Monte Carlo

• “Fitters”

• “Physics Interpretation”

14Particle ID ( )

u

x

E

t

Raw Data: , ,i pmt it x q

Signal Extraction

, , , , ,CC day CC ESCC NC ES

CC night eff eff

d d

dT dT

Reconstruction

2 2,sin 2 ...m Physics interpretation

Observables

-position-time-charge

Reconstructed event-vertex-direction-energy-isotropy

Photomultiplier tube

0i

in

x xt t

c

1 1 2 2 3 3( )2

( )( , ) ( , , , ) ( , , )

win

pmt d d dhardware drift

NE

g e RP r M r

, ,( , , ) ( , , , )dir dir i i fit fit i i i fit fit fitP r dL

1

141 1

2 1cos 9 20cos 2 35cos 4

( 1) 64

N N

ij ij iji j iN N

“Data Cleaning”• TABLE II: Number of events remaining in data set after each• step in the data processing described in Section 5.• .• Data Processing Step Events Remaining• Total event triggers 450188649• Neutrino triggers (hit multiplicity) 191312560• Analysis Nhit cut (Nhit > 21) 10088842• Low-level cuts 7805238• `Cherenkov Box' cuts 3418439• Fiducial volume cut 67343• Energy threshold (Te > 5 MeV) 3440• Muon follower cut 2981• Atmospheric followers 2928• Total candidates 2928

Extracting the Solar Flux

Maximum Likelihood Fit

CC NC ES

e

OR

CC NC ES

SNOconstrained 5.09 0.44

0.43(stat.)

0.46

0.43(syst.)

SNOunconstrained 6.42 1.57

1.57(stat.)

0.55

0.58(syst.)

• PDFs: kinetic energy T, event location R3, solar angle correlation cos sun

8B shape constrained fit: [in 106 cm-2 s-1]

No 8B shape constraint:

Assumption:No 8B shape distortion

Phase II (salt)July 01 - Sep. 03

Phase III (3He)Nov. 04-Dec. 06

Phase I (D2O)Nov. 99 - May 01

3 Phases of SNO: neutron (NC) detectionmethods (systematically different)

n captures on2H(n, )3H

Effc. ~14.4% NC and CC separation by energy, radial, and

directional distributions

40 proportional counters

3He(n, p)3HEffc. ~ 30% capture

Measure NC rate with entirely different

detection system.

2 t NaCl. n captures on35Cl(n, )36ClEffc. ~40%

NC and CC separation by event isotropy

36Cl

35Cl+n 8.6 MeV

3H

2H+n 6.25 MeV

n + 3He p + 3H

p3H

5 cm

n

3He

What does it mean to calibrate?

• Determine unknown parameters in the Monte Carlo. In SNO, these are almost all optical constants.

• Measure how well we reconstruct position, direction, energy, isotropy as a function of position in the detector and calendar time.

In SNO, the calibration effort dominates the analysis. Typically 90% of the analysis effort is used to calibrate, measure backgrounds, and understand systematics; the signal extraction is quite standard. Improvements in the analysis come about because of improved calibration.

SNO Detector LivetimePhase III Livetime: Nov 27, 2004 to Nov 28, 2005

Dec 1/05 Mar 1/05 Jun 1/05 Sep 1/05 Dec 1/05

RUN TYPE # OF DAYS PERCENTAGE ======================================== NEUTRINO 249.58 68.19 SUPERNOVA 0.14 0.04 CALIBRATION 89.26 24.39 OTHER 14.47 3.95 NO RUN 12.55 3.43

Calibration Source Manipulator

Radon/Light Barrier

Accuracy

< 2 cm single axis

~ 5 cm triple axis

Remote Operation/Interlocks

Stringent Cleanliness Requirements

Umbilicals Manipulation Detector Interface

337,365,386,420,500,620 nm wavelengths

45 Hz Pulse rateIntensity dynamic range about 1e7600 ps pulse width

Optical Analysis d d a a h hd d d

ij i ij ij ij ij jN N R T L e Number of in-time hits in run i and pmt j = (Number of photons emitted in run i) x

(solid angle of pmt j and run i) x (pmt angular response) x (transmssion through acrylic) x (laserball intensity distribution) x(efficiency of pmt j) x (transmission through water and acrylic)

d d a a h hi ij ij ij ijij

o oj oj oj oj

N R T LO e

N R T L

Remove unknown individualPMT efficiencies with “occratio”

Typically 40 runs x 7000 pmts = 280,000 data pointsFit for about 400 parameters:

, ( ), ( , ), , ,i d h aN R L

Optical AnalysisD2O Attenuation H2O Attenuation

PMT calibrations, PMT angular response, D20, acrylic,H2O

PMT Angular Response

Swapped pmts- angle of rotation